摘要:

AbstractThe response of the epidermal melanocyte population to repeated ultraviolet (UV) exposure (wavelength spectrum 275–350 nm) has been investigated in the crested newt,Triturus cristatus carnifex. The effects of different doses of UV light were studied. The animals were killed 7 months after the first UV exposure. Only a slight decrease in the number of pigment cells was found after 85 sequential irradiations with a total dose of 1.3 × 105J/m2, whereas striking decreases were observed when the same total dose was fractionated into 14 exposures or when a double dose was given in 57 exposures. The relationship between the square roots of the epidermal melanocyte densities and single doses appeared to be roughly linear, at least over the range of doses administered. The main factor in melanocyte damage seemed to be the single dose of irradiation rather than the cumulative dose administered. Decreased melanin content of the keratinocytes was observed in most irradiated anima

ISSN:0022-104X    

DOI:10.1002/jez.1402190202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe possibility that maternal RNA may be localized in specific oocyte regions was examined in fully grown oocytes ofXenopus laevis. These oocytes were subdivided into six regions perpendicular to their animal‐vegetal axis. Each region was analyzed to determine the amount of total cellular RNA, poly(A)+RNA, and newly synthesized ribosomal RNA. As would be expected from current evidence, total cellular RNA was found to exist in a gradient‐like fashion, highest at the animal pole and lowest at the vegetal pole. However, poly(A)+RNA and newly synthesized ribosomal RNA had significantly different spatial patterns from each other and from total cellular RNA. In addition, evidence suggests that newly synthesized ribosomal RNA requires two to three days before it is uniformly distributed within the oocyte. These results suggest that a mechanism may exist to create different spatial patterns for different classes of

ISSN:0022-104X    

DOI:10.1002/jez.1402190203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractEpididymal spermatozoa were maintained at 4°C during and after release from the epididymis to assess the effect of membrane fluidity on acquisition by the sperm of the ability to bind to zonae pellucidae of mouse eggs. The hypothesis to be tested was: If membrane fluidity is necessary for acquisition of the ability to bind, then exposure of sperm to 4°C to reduce fluidity markedly should lead to a characteristic delay time in acquiring the ability to bind to zonae. This result was not observed; instead, the relative extent of binding measured at 37°C was decreased relative to control by preincubation at 4°C. The relative extent of binding was reduced to 43% of control after 15 min and to 20% of control after a 60‐min preincubation at 4°C. The loss of binding ability was not reversed by subsequent exposure to 37°C in the insemination mixture for up to 60 min if fresh sperm were dispersed directly from epididymides into the cold medium. Dispersal of sperm into medium at 37°C followed by a 15‐min preincubation at this temperature, during which time sperm acquire the ability to bind to zonae, conferred full protection against cold‐induced loss of binding ability. This loss could not be attributed to motility effects: Mouse sperm are completely immotile if cooled to 4°C, but fully regain their original motility upon warming to 37°C, the temperature of the insemination medium. The binding sites on the sperm plasma membrane for the zona pellucida appear to lose irreversibly their binding ability at 4°C with a half‐time of about 15 min. These results suggest the hypothesis that rearrangement of binding site subunits is involved in the acquisition of the ability to bind to zonae, rather than long‐range interaction of plasm

ISSN:0022-104X    

DOI:10.1002/jez.1402190204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe effects of temperature acclimation on (1) fiber‐type distribution, and (2) alternate metabolic fuels for energy supply within different skeletal muscle fiber types in striped bass (Morone saxatilis) were examined. Histochemical analysis demonstrated an increase in the proportional cross sectional area of oxidative red fibers from 9.03% to 15.03% during cold acclimation (25°‐5°C). The rate of oxygen consumption was 1.78 times greater in red muscle than white in 25°C acclimated fish. This ratio increased to 2.32 in 5° fish. Oxidation of both14C‐U‐glucose and14C‐1‐palmitate was significantly greater in red muscle than in white at both acclimation temperatures. A lack of thermal compensation for metabolism of14C‐U‐glucose was exhibited by both fiber types. Red muscle showed a dramatic increase in rate of14C‐1‐palmitate oxidation after cold acclimation. Activities of glycolytic enzymes confirmed a high glycolytic capacity in white muscle; glycolytic capacities were dependent on acclimation temperature in both fiber types. Only red muscle showed a positive compensation for activities of key enzymes from aerobic metabolism. The results indicate an increasing reliance on aerobic metabolism of fat in the swimming musculature at cold acclimation temperatures. The capacity for sustained swimming under these conditions is conserved by (1) an increase in the relative proportion of red fibers, and (2) an enhanced capacity for energy supply in the red muscle by oxidative met

ISSN:0022-104X    

DOI:10.1002/jez.1402190205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe in vivo blood oxygen binding properties of rainbow trout were studied in normoxia and hypoxia (P O 255–60 mmHg). Owing to hypoxia the in vivo oxygen dissociation curve of blood was shifted to the left; the P50value decreased from 37 mmHg in normoxia to 27 mmHg in hypoxia. Hypoxia also caused an increase in the erythrocytic volume, a decrease in the concentrations of ATP and hemoglobin inside the cell, and an increase in the intraerythrocytic pH. All these responses are interrelated. The swelling of the erythrocytes decreased the concentrations of ATP and Hb in the cell. This decrease changed the Donnan distribution of protons across the red cell membrane, thus increasing the intraerythrocytic pH. The increase in the intraerythrocytic pH was the main cause of the increase in the blood oxygen affinity. Owing to the increased blood oxygen affinity the oxygen transport from gills to tissues in hypoxia was only slightly decreased from that in normoxia. However, as the venous oxygen tension decreased in hypoxia, the diffusion of oxygen from tissue capillaries to the cells was probably slowed down in hypoxia when compared to nor

ISSN:0022-104X    

DOI:10.1002/jez.1402190206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractTotal oxygen uptake in the blue crabCallinectes sapidusdoubles with a rise in ambient temperature in the range 15–25°C, and increases precipitously (Q10=4.92) in the range 5–15°C. Both systemic and cellular phenomena are responsible for the pattern. At summer temperatures, where motor activities are maximal, the oxygen affinity of blue crab hemocyanin is low, and considerable volumes of oxygen are delivered to the tissues. At winter temperatures, where feeding and locomotion virtually cease, the hemocyanin‐oxygen (HcO2) affinity is so high that little oxygen can be extracted by the tissue and O2is transported entirely in the free form. At the transitional temperature of 15°C, a seasonal acclimation of HcO2affinity permits appreciable oxygen delivery to the tissues in the spring, but curtails oxygen delivery in the fall.Both muscle and hepatopancreas utilize the hexose monophosphate shunt (HMS) in carbohydrate metabolism. Specific activities of the enzymes participating in the HMS are greater in hepatopancreas than muscle, and the sensitivity of O2uptake to the glycolytic inhibitor iodoacetate (10−2M) is smaller. The temperature dependence of O2uptake in the range 15–25°C is much smaller in hepatopancreas than in muscle. The ratio of C‐1/C‐6 labeled glucose utilization indicates that, at low temperature, the activity of the HMS in hepatopancreas is five times greater than that of glycolysis. Thus, the low thermal sensitivity of O2uptake in hepatopancreas appears to be due to a change in the relative contribution of the two pathways to total carbohydrate metabolism.There is no evidence of a compensatory response of intermediary metabolism in muscle, which comprises the major fraction of total biomass. The thermal dependence of O2uptake by the animal exceeds that of either hepatopancreas or muscle, due to the large increase in HcO2affinity, and hence a decrease in tissue O2supply, a

ISSN:0022-104X    

DOI:10.1002/jez.1402190207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe effects of acclimation temperature on hemocyanin‐oxygen (HcO2) transport were examined in two species of decapod crustaceans representing different geographic and thermal ranges. In the coldwater speciesCancer borealisand the warmwater speciesMenippe mercenaria, the performance of the HcO2transport system is maximized at 15 °C, a summer temperature in the northern habitat and a winter temperature in the southern habitat. InC. borealislittle unloading at the tissues occurs at 5 °C, and inM. mercenariaoxygenation at the gill is incomplete at 25 °C. The temperature coefficients describing rates of ventilation, heartbeat, and total oxidative metabolism fall within a narrow range (Q10= 1.9−3.6), providing no indication of ventilatory or cardiovascular adjustments that would allow the HcO2transport system to function at the maximum level at different temperatures. Comparison of the HcO2equilibrium properties suggests that HcO2affinity has been selected for a particular thermal range, but not cooperativity or pH dependence. The thermal limits of the O2transport system are set by both the direct effect of temperature on HcO2equilibrium and the indirect effect via the Bohr shift that accompanies the change in blood pH with tempe

ISSN:0022-104X    

DOI:10.1002/jez.1402190208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractEvidence is presented demonstrating that in the dogfish,Squalus acanthias, D‐glucose is transported from the blood to the ocular fluid compartments by a mechanism that is consistent with carrier‐facilitated transport. Across the dogfish aqueous barrier D‐glucose is transported 8.4 times faster than L‐glucose, whereas this D/L transport ratio is only 5.5 in the rat. Similarly, the D/L transport ratio is 12.7 across the dogfish vitreous barrier and only 6.1 across this barrier in the rat. It is estimated that per unit area of vitreous barrier, the rat transports D‐glucose faster than the dogfish but also has a greater passive permeability, as measured by L‐glucose, and transport is therefore less efficient. Urea transport was found to be faster than L‐glucose transport, suggesting a transport mechanism for urea other than simple diffusion. The sectional analysis of frozen vitreous humor indicated that the lens of the dogfish is supplied with D‐glucose from both the ciliary epithelium and across the retinal pigment epithelium, while the retina receives D‐glucose primarily across the p

ISSN:0022-104X    

DOI:10.1002/jez.1402190209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractIn order to elucidate the mechanisms of neurogenic control of bone devlopment and growth, the effects of traumatic and electric stimulation on the development, size, and shape of antler bone tissue were investigates. Unilateral growth of antler in a female deer was initiated after traumatic stimulation of the frontal bone. Electrical stimulation of antler nerves or antler periosteum resulted in an increase in more than 70% in antler length and over 40% in weight. Stimulation of antler nerves also resulted in abnormal shape of antlers. The role of periosteal nerves and the participation of the central nervous system in the responses to stimulation is discussed.

ISSN:0022-104X    

DOI:10.1002/jez.1402190210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractOn either side of Hensen's node of the fully extended primitive streak of the chick embryo (stage 4) the mesoderm is already organized into circular domains called somitomeres. As Hensen's node regresses, paraxial somitomeres are added in tandem and are early morphological representatives of metameric pattern in the mesoderm. These organized circular domains of mesenchyme cells are best visualized with stereo pair scanning electron microscopy. Experiments suggested that a prepattern of segmentation exists in and around the fully extended primitive streak. Streaks divested of Hensen's node can generate some paraxial somites, but only if surgically split down the midline. We assessed metameric pattern formation in nodeless streaks, both severed and unsevered down the midline. Operated blastoderms were cultured 15 hours, fixed, dissected, processed for scanning electron microscopy, and photographed in stereo. Split nodeless streaks produced a cranial to caudal sequence of somitomeric development. This sequence is similar to the sequential maturational events seen in the segmental plate of older embryos. The least mature somitomeres, toward the posterior end of the severed edge, appear as circular domains of radially oriented cells, looking much like the first somitomeres to emerge near Hensen's node of the stage 4 streak. More cranially along the severed edge, somitomeres are morphologically more mature, being more condensed, with cells oriented about a central myocoele. At the most cranial end of the severed piece, somitomeres are the most mature, having contracted about their centers to create intersomitomeric gaps that permit their identification with light microscopy as individual “somites.” Embryos from which the node was removed, but the streak left intact, generated only the most primitive somitomeric pattern repetitively along either side of the primitive groove. We conclude that regression of Hensen's node provides for the timely initiation of morphogenesis of somitomeres from a prepattern of segmentation that already exi

ISSN:0022-104X    

DOI:10.1002/jez.1402190211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY